Gearboxes

[Blatman]

I think that with the MT75 you will have no choice if the gearing is wrong. All you'll be able to do is change the diff ratios, which is not really the fine tuning you should be looking at to get the best from what you have. The type 9 has far more choice, both in ratios, and in strength of materials used for the gears etc.

IMO the 0.761 fifth with 3.62 will see a theoretical top speed in excess of 150mph, but I think you'll find yourself needing to change down to 4th on long hills just to get up 'em. 130ish mph is a practical max. speed for a car with a screen. Aerodynamics mean you need LOTS of horses to get much beyond this.

Stick with a "standard 0.9* 0r 0.8* 5th, and look for a 2.9 or 2.6 1st. That will keep the intermediate ratios close, and make for swift progress.

[Sooty]

Don’t forget I’m talking diesel here, it’s all torque and low revs, and I’ll be keeping the red line about standard, which is around 4600rpm. To give you an idea the Audi A6 that the engine came from has an official top speed of 140 at 4500rpm, as sixth gear is 33.5mph/1000revs. But don’t forget this engine at the moment is making 45% more power and torque, so I doubt I’ll have to change down

For ref I want to fit aero screens, and I've been using .72 for drag calcs, is that about right?

I agree a first gear around the 2.6:1 seems about right to me too but fifth with a 0.9:1 would mean I’ll be doing about 95mph at red-line (50/15 tyres)

Which does beg the question that I hadn’t really thought of before, at what speed would I not want to be in a westie? This is ignoring track use, but on a road, at what speed does the wind/exhaust/wife screaming to slow down get too much? Then at least I’d have a target top speed to aim at, I’ve been trying for 140/150mph, which now thinking about it may be a tad high  

[Blatman]

I had considered a 5,500rpm red -line. As yours is a lot lower, I'll leave you with the long fifth gear. Comparing top speed for the engine in a totally different car is irrelevant.

I don't know enough about torque versus power WRT overcoming drag (I have no idea what the Cd of a Westfield is, but it is HIGH. Less so with aero's, but it's no jelly mould), and not having a screen will definitely help, but gut feeling says you'll be changing down..........I'll stand to be corrected when it hits the road.......

I know of only 1 Westfield that will pull 150mph, and it's this one. 350+bhp, LOTS of torque. It's a monster.

As for noise, wear ear plugs, especially on a journey down a motorway or A road for longer than an hour. It makes a world of difference. I was resistant until I tried about a year ago, and now I never leave home without them.

[Edo]

Sorry to butt in folks - but what would a 4 Speed RS2000 gearbox be, is that a type 9?

[Sooty]

I use a little program called car test, into which you add in as much data as possible, from engine characteristics, gear ratios, size, weight, type of car. You can get in pretty deep with info such as type size weight, fiction co-ef, tyre temperature  (when hot)  and road temperature etc.

From previous projects experience I’ve found it to be moderately accurate, the most it’s ever been out from a hypothetical quarter mile to an actual one was about a quarter of a second.

The 0.72 drag factor is from a C*****m (think that’s how you spell it) which should be about the same.

With regard to top speed the programs showing a time/speed curve with a very sharp start (as you’d expect) then as you get faster it rounds of when the torque takes over from the horse power which seems to be about the 110mph mark, from then on it’s more of a push towards 140mph, if that makes sense.  But at the moment I’m still open to suggestions about a realistic top speed that I should be aiming for, one thing is for sure is that if I have to fit that front wing to be stable at that type of speed I’ll not go above 100.

Edo, the more the merrier as far as I’m concerned, I’m still learning about Fords, all the cars I’ve played with so far have been VW/Audi (I won’t count my first car which was an Allegro – no laughing) I’ll do some digging on the ES2000 and check which box was fitted. This engine won’t know what hit it, it started life off with a six speed box, I’m just glad ford don’t make a three speed  

[Blatman]

Realistic top speed would be between 130-140mph. You don't need the front wing for stability. That car is a hillclimber/sprinter, but was originally built for the British GT Series........

If you say that speed/acceleration drops off when the torque takes over, then it'll be horses you need to push through the 130mph barrier, which is what I suspected. I have a reasonable amount of exprience with Westfields, with lots of engine configurations, and almost without exception, top speeds are always around the 130mph mark. I have no experience of the VAG V6, but, even if it produces good horsepower, how much will it add to the mass of the car as a whole? I bet it weighs quite a lot, hence my scepticism about what a performance simulator will give you compared to real world experiences. I know of a 270ish bhp Vauxhall powered c******m that will get above 140mph (in 15 secs too! ) but it will be a lot lighter than your car (it weighs under 500kg's), and has the appropriate gearing (in this case, a 1.1 6th gear, or it was. It's been changed recently...... There is an mpeg at www.the-webbs.com/k2rum/k2frames.htm of the 141mph run..........) This car is an extreme example, but it shows that even with this amount of expenditure, top speeds higher than 140mph are difficult to come by in a Sevenesque car.

Is the TDi a turbo?

[Sooty]

The actual top speed as you can imagine will only be used on the very odd occasion typically when I take it over to Germany, and only then to see if it will do it.

I haven’t got the actual weight to hand at the moment, but I remember that it’s about 8kg lighter than a Rover V8, which is what I’ve been basing certain figures on. I’m guesstimating the cars wet weight will be around the 700kg mark.

But don’t forget the torque, and what effect that can have on weight, my current every day car (MKIII Golf TDI  tuned to 187hp) has a 0-60 time of 6.52 seconds with just me in, the 0-60 time with four people was recorded at 7.24 seconds, that’s all the penalty was for an extra 250kg (approx) – although the hardest part was getting the strip to let me run with four people in the car. They refused to let me tow the trailer, which would have been another 370kg

Is the TDI a turbo? - The engine in it’s original Audi tune is a turbo charged 2.5ltr, V6 making 180hp/273lb. In it’s present state with custom chips, dual turbo and honed fuel injectors it’s been bench dyno’d at 260hp/408lb and that’s with a reduced boost and fuelling mix to make it really clean emission wise, without the restrictions on it’s been measured at 342hp/493lb. But I don’t really want to run it at that high a state of tune for any length of time as it does induce a little more fatigue. Although I could go up to 300hp/450lb without any reliability problems and the emissions would be similar to the original engine, but I thought I’d be a good boy – and make life a little easier o the gearbox at the same time.

For ref my calcs indicate that a 780kg westfield (inc me) would reach 140mph in 37.3 seconds, having made 60 in 3.56, 100 in 8.11 and a quarter mile of 11.60 – traction permitting. But that is with a 300hp/450lb engine tune, before I had only been checking out the theoretical gear ratios, I didn’t run the analysis tool, which I have just done and the 260hp tune would only have theoretical top speed of  133mph

My normal driving won’t get anywhere near that type of speed so thinking practically I think I’ll try to keep as close as possible to the original Audi ratios, which means 70=2010rpm, 90=2670rpm, 120=3520rpm. Which should be sweet as the real power band is from 1600rpm to 4300rpm.

Cheers for the C******m link, it looks great, unfortunately the videos don’t seem to be available at the moment, I’ll try again later.

[Blatman]

It would seem my gut feeling on your 260bhp was about right then.......

At 780kg's, your car would be considerably heavier than most Seights, despite the engine weighing 8kg's less  I'm guessing you are including the extra weight of intercooler(s) and such like (where you gonna put 'em?). It would probably not pull the 0-60, 0-100, or 1/4 mile times you quote. At Brooklands last year, the Arnie Webb VX best 0-60 was around the 3.6-3.8 mark using soft compound ACB10's, with gearing that is properly specced for that sort of performance. With an MT75 or type 9 with standard ratios, you won't get anywhere near........It's not all about horsepower and torque, don't forget.

I'm hoping Ian Crocker will be along in a minute to help me out here, but there are plenty of seights with similar power, but less weight, that would struggle to make those times. It is not my intention to p*** on your chips (although I'm doing a pretty good job. Sorry), but I think that raw data input to a performance programme is too far removed from real world situations to be of much value.

[Sooty]

I’m guessing 700kg for the car, the rest is me and all the thermals I’ll be wearing  When guesstimating that type of thing I’d rather err to the worst case scenario, that way I’ll always be pleasantly surprised with the real figures. What type of weight would the average SEight come in at then?

I’m inclined to defend the 0-60’s, a well-tuned diesel will out pace a similar spec’d petrol to at least 0-40, from then on the petrol should start to pull back. I was at GTI International a few weeks ago, when VW Motorsport put two of the VW Cup racers up against each other the first was a 220hp Beetle RSi the second a 200hp Golf TDI-R. Both times they raced, the diesel won, a friend is meant to be posting the video of it soon, I’ll send you a link when it’s available. The TDI’s initial pull from the line is so much better than the RSi.  

I’m well familiar with ACB10’s I use the 195/4515’s on my golf for track days, I love them for their stickiness. The gearing figures I used on the example were the original Audi spec’s. I am well aware that any of the performance times are reliant upon getting the power down to the road, I’ve read a few comments about which shocks/springs to use elsewhere on the forum and I have always intended to fit a Quaife ATB diff, I have in my Golf and love it. Although I’ll welcome any points you may want to add in that department.

I’ve got no problem with you questioning the program, up to now it’s served me well, but it’s not a bible. I use it as a guide, the reason I’m here is to learn and get things right, which is why I appreciate you debating the points. Hopefully it will save me time and money for when it all comes together, and if I learn things on the way even better. In it’s defence the program has been a very good indicator (for previous cars), the key is to put real data in to get believable results out. I have real engine data to play with, but with the car details I’ve been using have been from a C******m and I’ve been assuming similar performance. The program just applies basic physics and maths, the only thing that it assumes is that the driver is going to change gear at certain points and not fluff anything, which none of us have ever done – not.

Take a look and have a play, if you see anything obviously wrong in the C******m assumption then I can always adjust the figs.

[Blatman]

There are some figures posted around here somewhere (I can't be arsed to go find 'em ) on Seight weights, but I think they come in at around 650kg's, without too much attention to weight saving. My narrow bodied hillclimb car with a N/A cossie (ie, an engine that weighs as much as the V8) comes in at 585ish Kg's (It has seats harnesses, some carpet, a screen, wipers etc etc, and is fully road legal. Actually there's a picture here. I've changed the wheels for lighter ones since this pic was taken). At 700kg's, yours would be 15%+ heavier, with only around 20 more (<10%) bhp. This puts you at a power to weight disadvantage..........

I've had my sceptics hat on during these postings, and as I say, I have zero experience with modern diesels, unlike you. With my sceptics hat still firmly on though, I'd say the VW sponsored performance test could well have been weighted in favour of the diesel, if that was what the test was supposed to be promoting. For a start, why didn't they put the diesel Golf against another Golf, rather than a Beetle (and yes I know a Beetle is just a Golf in a 60's dress  )? The aerodynamics and vehicle dynamics must be different enough to make the test nothing more than a publicity stunt.

If the car test program has specs for a c******m, then assuming thay have been loaded from a reliable source, they should be good. FWIW, I have never seen the results of a c******m wind tunnel test, if any have been done, which have given the exact drag coefficient as you would expect to see from a major manufacturer. I am aware of some wind tunnel tests done on a c******m which was testing some aerodynamic additions (long front cycle wings, and a rear diffuser, IIRC), but I can't remember if a base line Cd was acquired or published, although if they were testing additions, I should imagine a baseline was taken to see if there was any significant change. If I can find it, I'll put it up.

As for the Quaiffe ATB, I have one. I love it too. Good choice, as long as you keep both wheels on the deck. Kerb hopping in anger on a track is a no no.

I'm learning too, and welcome the chance to debate new subjects. This has been an interesting few days. I hope you get it built into a nice car, and I hope that you are able to disprove my misgivings. If you do, I'll be the first to congratulate you on a job well done. Good luck with what sounds like an interesting project.

Just where will the intercooler go though?    

[Sooty]

I may have been a little pessimistic on the weights, but I don’t in tend to get too hung up on exact figures. The only ones I know that are correct at the moment are the engines, all others have either been guesstimated or calculated, which to my mind always means the figures are approximate, and shouldn’t be taken as gospel

Good pics of the car, what wheels are you using now then? I’m thinking of OZ Superleggera’s

As far as the VW thing goes, it wasn’t a setup, I know some of the people on the VW Motorsport team, they were genuine races.

The intercooler will be just in front of the radiator, separated by about an inch gap, I have a friend who can make up an ali intercooler & radiator to fit. Thankfully VW diesel engines don’t run particularly hot, so radiated heat soak when stationary shouldn’t be a great problem and since I intend to use the vented nose cone, I believe that side of things should be OK.

[Blatman]

I'm using K&N Minator's, in 13"x6". They look like Minilites, and saved me a total of 28kg's over the wheels in the picture. Losing 7kg's per corner of unsprung weight made a significant difference! If I was looking for 15" rims then the Superleggeras would be my first choice. They're very light, and look good too. I'd recommend 15"x7", with 195-50 tyres. That's what the green car runs, rim/tyre size wise. They look good and fill the arches nicely.

You've obviously done some homework on the installation of the intercooler and rad, and you clearly know the engine well. Good luck with the build. I look forward to seeing it.

[Sooty]

Tyre wise I was thinking of ACB10’s (195/45/15) which should help in the traction stakes.

I’ve had intercooler/rad units made up before they can work really well, typically they are much more efficient and when made properly much better airflow to help the turbo.

Thanks for all the info and guidance